Learning outcomes of the course unit
The student will be expected to: develop the capacities to resolve the most common veterinary problems using epidemiological methods; acquire the basic principles and the most commonly applied epidemiological techniques of veterinary medicine; apply a quantitative reasoning method, focusing particularly on disease frequency estimates, test assessment and risk factor assessment.
Course contents summary
1. Introduction to the study of epidemiology
Historical considerations and basic concepts. Differences between epidemiology and other diagnostic disciplines. The concept of disease determinant. Primary determinants. Secondary determinants. The concept of "population". Levels of populations.
2. Tasks and aims of epidemiology
Tasks of veterinary epidemiology. Prevention, control and eradication of diseases. The aims of epidemiological studies. Observational and experimental studies.
3. From association to causality
Demonstration of causality in observational studies. Statistical significance and causality. Chi-square test for comparing two percentages. Statistical significance tests. Association and causality: types of association. General model of causal and non-causal associations. Examples of causal and non-causal associations.
4. The epidemiological approach to the causes of disease
- Henle-Koch postulates. Evans postulates. The Rules of John Stuart Mill. Demonstration of causality. Criteria of causality. Prospective (cohort) and retrospective (case-control) studies for demonstrating causality. Prevalence rate, relative risk and odds ratio.
5. Biological variability: basic concepts in epidemiology
Frequency distribution. Cumulative, median and centile frequencies. Central tendency indices. Variation indices.
Aims of sampling. Characteristics of a good sample. Sampling errors. Sampling methods. The variability of an estimate and confidence limits. Sample size.
10. Measuring disease frequency
General concepts. Morbidity and mortality. Survival and lethality. Prevalence and incidence. Attack rate. Relationship between incidence and prevalence. Epidemic, endemic and sporadic diseases. Other methods for measuring disease frequency. Measurement standardisation.
11. Screening tests for sub-clinical diseases
Population screening. Test performance assessment. Sensitivity, specificity, positive and negative predictive value. Methods for improving the predictive value of a test. Multiple tests: use of 2 tests simultaneously or in succession; serial or parallel interpretation. Concordance index between two tests.
12. Transmission and maintenance of infectious diseases
Transmissible diseases. The cycle of a transmissible disease. Latent infection and carrier status. Horizontal and vertical, direct and indirect transmission. Host types. Mechanical and biological vectors. Factors associated with the spread of infections. The spread of infections and host characteristics: receptiveness and contagiousness. The spread of infections and agent characteristics. The spread of infections and contact efficiency. Routes of infection. Transmission modes. Long distance transmission of disease agents. Vertical transmission of disease. Maintenance and survival strategies of the agent.
13. Disease patterns
Epidemic curves. Kendall’s threshold theorem. Epidemic trends. Common source and propagation epidemics.
14. Models in epidemiology
Model types and functions. A classic model: the Reed & Frost model. Bovine Neospora caninum Infection: example of a mathematical model.
PRACTICAL LEARNING ACTIVITIES
- With the help of the computer, students will consolidate the concepts acquired during the theoretical lessons, by solving problems relative to
BOTTARELLI E.: VetEpi * Quaderno di Epidemiologia Veterinaria. http://www.quadernodiepidemiologia.it.
AHLBOM A., NORELL S.: Epidemiologia moderna. Il Pensiero Scientifico Editore, Roma, 1993
BEAGLEHOLE R., BONITA R., KJELLSTROM: Epidemiologia di base. Italian edition by G. Agazzotti, Editoriale Fernando Folini, Casalnoceto, 1997.
PFEIFFER D.U., Veterinary Epidemiology - An Introduction. Institute of Veterinary, Animal and Biomedical Sciences, Massey University, New Zealand. Available online from the following address: http://epiweb.massey.ac.nz/ epinotes.pdf